The problem you face with the BB further suggests that the frame is Carlton/Sun/Raleigh in origin. These frames frequently sported Raleigh standard threading BITD, which is 1.370" x 26TPI. Hence your cups will screw in a couple of turns and then bind.
The BB threads in my Sun frame have 26TPI Raleigh threading - as does the headset. I believe that your frame/fork came without headset so if you have a standard 24 TPI lockring to hand then try screwing one down to see if you encounter the same issue. I expect that the fork steerer will also have a 26TPI thread.
Nobody(*) makes 26TPI stuff anymore so you're best off placing a WTD ad here or looking on ebay. Fortunately the headsets and BBs of this era tend to last pretty well so you can fairly safely buy used and replace the bearings. You could ask this guy:http://oldbiketrader.co.uk/
if he has any NOS parts in stock at the moment. Also bear in mind that no (or at least very few) cotterless BBs were available in 26TPI. You can normally swap out a cottered spindle for a cotterless one, but be prepared for trial and error! Or use a cottered crank, which are cheap and plentiful on ebay.
(*) Phil Wood offers 26TPI cups for his sealed BB, but that's probably a bit beyond your budget.
Many Thanks Gareth - i'd read Sheldon Browns www and saw that raleigh / carlton etc. used a separate standard at the time and it had crossed my mind that I might need to go down that route but took the sellers word on what was needed. Don't want to go down the cottered crank route as am planning a fixed wheel build for this hopefully with some decent 2nd hand track components. so problems ahoy I reckon. As for headset, I was 'advised' that this will require a 30mm headset which is JIS standard I believe - therefore adding a little more confusion to the frames origins!
I'll look at the www you kindly provided and see if any light can be shed on what I need to get my mitts on before I commit further into this build - the way it's going it may just not get off the ground. As for Phil Wood components, I don't dare look else my 'cheap build' could end up like all my others - vastly over budget